So while, yes, “on a larger level I’m talking about that,” Porter’s song has typically multiple layers. Musical Genocide isn’t the only song on his acclaimed third album Liquid Spirit that talks about the record industry. “If you manufacture everything; if you shy away from the organic artist who’s gone through something in his life to try figure out music; if you’re only going for the sexiest, newest thing… Well, that’ll be the death of blues, of soul… So that’s what I mean.”

Luckily, this charismatic Californian is here to breathe life, and vitality, and fun, and excitement, and passion, and honesty into the musical genres he has loved from boyhood, ever since Nat “King” Cole entered his heart. It’s the central message of the album’s title: Porter is here with Liquid Spirit, offering up a replenishing, satisfying brew. As the 200,000 fans who’ve bought his albums in Germany will attest, or as the British listeners who have heard him light up the airwaves at 6 Music and BBC Radio 2 will agree, or as the lucky crowds who’ve seen him at Cheltenham Jazz Festival or playing with Gilles Peterson or his set just before Stevie Wonder at Calling Festival can vouchsafe: you can drink deep of Gregory Porter. And the best kind of intoxication will follow.

As the lyrics to his foot-stomping, high-clapping title track have it: “Un-reroute the rivers, let the dammed water be, there’s some people down the way that’s thirsty, so let the liquid spirit free…’”

It’s a sentiment that’s of a piece with the slow burning success of Liquid Spirit, released last autumn as the first fruits of Porter’s new worldwide deal with Blue Note Records, and now back in the UK mainstream charts and nearing the Top 10.

“The word-of-mouth quality of this record, and even my first two, is a positive thing in a way,” affirms this big-voiced, big-hearted man who’s as adept at covers of The “In” Crowd and jazz standard I Fall In Love Too Easily as he is at singing his own compositions. “When you say the people are thirsty – they want something. And not speaking narcissistically, everything they want is contained in me! But I do know that people are thirsting for something musical. And they come to me after a concert and say: where you been?’ And sometimes,” he acknowledges with a grin, “I think they don’t even mean me – it’s a feeling they get inside once they hear something I’ve done.”

Where he’s been is slowly, measuredly building his craft. It’s a work ethic – dogged, patient, respectful – that Porter learned at his mother’s knee in Bakersfield, California. A single parent to eight children, and a “storefront minister”, she’s paid tribute to on the simple, elegant, brushed-snares album track When Love Is King: “He lifted up the underneath, all of his wealth he did bequeath… of hungry children first He’d think to pull their lives up from the brink…”

“These are all concerns she’s had, the philosophies she instilled in me. If there was somebody on the edge who needed just a little help to get back, whether spiritually, food, housing, clothing… That was her thing. She as a storefront minister who wanted to go where people are dazed and confused and lost. Kids walking around who didn’t know where their daddy was. She wanted to go where there was trouble.”

Often times that trouble rolled right up to the Porter kids’ front door. The Klu Klux Klan was active in Bakersfield, and young Gregory and his brothers regularly ran the gauntlet of racial hate.

“It was intense,” he says simply. “But my mother protected us and shielded us from that – psychologically as well. But at the same time we still had cool friends, basketball games and summer league. So there were two kinds of worlds going on.”

There were also many musical words. Bakersfield was an epicentre of country music. But it’s mostly migrated population – from Texas, Louisiana, Arkansas, Mississippi – had also brought with it gospel, blues, rhythm and blues, jazz, soul.

“I was singing that music of a bygone era with these old church members that my mother would associate with. And that still informs my music. Liquid Spirit is directly from that.”

This rich mixture goes some way to explaining the power and impact of Porter’s music. But he’s the first to admit that it also means it can be confusing to purists.

“I’m fully aware that everything I do doesn’t adequately please jazz traditionalists,” he says with a shrug. But he likes it that way – likes being able to appeal to the Cheltenham Jazz crowds and the younger fans of Peterson, the respected, genre-hopping DJ doyen.

“I laugh at the mix of people who show up at shows. I realise I have to give them all something – and something for all of them exists in me. There are songs that a 68-year-old grandma likes. And there are hard-hitting, more bass- and funk-infused things. That’s part of my vocabulary as well. And I don’t do them as a separate part of the show – they co-mingle and co-exist. Which is something I’ve done with everything – racially, politically. I’m trying to find that happy medium.”

All of which has conspired to take Gregory Porter a long way from Bakersfield. These days he lives in Brooklyn with his wife and 18-month-old son. But, actually, mostly he lives on the road.

“It’s intense,” he nods of the familial absence that’s been amplified by the international success of Liquid Spirit. “It’s intense,” he repeats. “I go home and he tries not to let me go the day that I’m there. He knows that if I have a 5am wake-up for a flight, he knows I’m up and liable to be gone for two, three weeks. And that’s a long time in his memory. That’s half his life!

“But one thing I’ve realised is that with all three of these records, I don’t shy away from uncomfortable or painful situations in my life. So that’s the emotions that that brings. Today, before I came here, I was working on a song called Cornbread And Caviar Dreams, which is about my son. My wife is Russian, and of course my mother made great cornbread,” he laughs. “So that’s painful. But I’m figuring it out. I want him to hear the message in When Love Was King. I hope he has thought and empathy for other people, and mutual respect. He has some say in this record.

And true to his positive mindset, Porter uses the separation, and the travelling, and alchemises it into something magical on stage.

“In a way, jetlag and the punishing schedule can actually take me there more,” he says of his onstage mindset. “The band will be like, ‘Greg, you ain’t got to sing that hard!’ But that feeling of exhaustion makes me think of my family or my mother or a situation or a struggle. When I sing Work Song it makes me think of my mother and how hard she worked. And it makes me work harder.”

And when he’s not working, this stylish man is relaxing by entertaining in another way.

“I love cooking, and I love having friends over. I think of music in the same way I think about food, in the serving aspect – you put a plate of food in front of a friend and it feels good, they’re nourished. I think about music like that. And the things that I’m good at are these nourishing things – music, food…. I used to be into massage. Giving, not receiving! And then some other things that you don’t need to know about!” he adds with a hearty laugh.

But in the end it always comes back to the music. For Gregory Porter the songs, and their messages, and their power, literally are the be-all and end-all.

“I’m trying to come honestly, really trying to be unpretentious. I’m trying to be appealing, even as a jazz artist, to the non-jazz head. Trying to speak to them as well. I want to speak to the human heart.

“And I’m gonna keep on trying to do my thing,” he smiles. “Really, I’m married to music. And whether people keep on buying my records or not, or keep on coming to the shows or not, I’m still gonna sing. I’m amazed and thankful and blown away that I’ve had these opportunities. But if they take it away, I’m cool. I’ve still got my songs,” Porter concludes, beaming expansively. “I swear to God I am cool!”

That he is. They don’t come much cooler than Gregory Porter.